如何在表中创建一个按钮执行mysql查询

Question

I have a simple html table that displays data from a mysql table containing a list of available tournaments.

<table>
    <tr>
        <th>Tournament Name</th>
        <th>Platform</th>
        <th>Date</th>
        <th>Venue</th>
        <th>Judge</th>
        <th>Description</th>
        <th>Limit</th>
        <th>Register</th>
    </tr>
    <?php while($row = mysqli_fetch_array($result)):?>
    <tr>
        <td><?php echo $row['nTournament'];?></td>
        <td><?php echo $row['pTournament'];?></td>
        <td><?php echo $row['dTournament'];?></td>
        <td><?php echo $row['vTournament'];?></td>
        <td><?php echo $row['jTournament'];?></td>
        <td><?php echo $row['dTournament'];?></td>
        <td><?php echo $row['lTournament']; ?></td>
        <td><form method="post" action="tournamentlist.php"><button type="submit" name="btn_register"></button></form></td>
    </tr>
    <?php endwhile; ?>
</table>

What I want to do is that once the current user clicks that button, the button executes a query which takes the current user's id and the tournament id of the selected row to add them to another mysql table. Something like a tournament inscription. The query/function I want to run is:

if (isset($_POST['btn_register'])) {
    singup();
}
function singup() {
    global $db;
    $idUser = $_POST['idUser'];
    $idTournament= $_POST['idTournament'];
    $query = "INSERT INTO registeredCompetitor(idUser, idTournament) VALUES ('$idUser', '$idTournament')";
    mysqli_query($db, $query);
    header('location: tournamentlist.php');
}

The query works just fine on it's own but I don't know if the function itself works because of the button. Is it possible to do such thing without the use of a form? If not, What other ways are there to do something like this?

EDIT1: Button now is ready but nor the function or the query executes once it's clicked.

Answer 1

You can create a form on each row that has 2 hidden fields in it. Not sure what your DB fields are called though so you'll have to change user_id and tournament_id to something appropriate.

...
<td>
    <form action="post" action="the_name_of_your_php_script.php">
        <input type="hidden" name="idUser" value="<?php echo $row['user_id']; ?>">
        <input type="hidden" name="idTournament" value="<?php echo $row['tournament_id']; ?>">
        <button type="submit" name="btn_register"></button>
    </form>
</td>
...

Can't wrap it because <form> is not allowed as a child of <td>

All the documentation I see online permits forms inside of <td>. The other alternative is to use a link instead of a form.